Cathode-gated amplifying phase detector



June 20,1950 w, GRAY 2,512,495

CATHODE-GATED AMPLIFYING PHASE DETECTOR Filed May 16, 1947 2 Sheets-Sheet 1 Fig.

POSITIVE HIGH- l0 VOLTAGE DIRECT- CURRENT SOURCE CONTROL DEVICE SOURCE 9F EvEN HARMONI'CS OF FUNDAMENTAL SOURCE FREQUENCY CURRENT SOURCE JOHN W GRAY i I i 28 i I l 2/ I i (29 NEGATIVE HIGH VOLTAGE DIRECT- CURRENT SOURCE 1 I l i l l l l FUNDAMENTAL I ALTERNATING 3mm I i L. J

June 20, 1950 J. w. GRAY CATHODE-GATED AMPLIFYING PHASE DETECTOR 2 Sheets-Sheet 2 Filed May 16, 1947 Fig.2.

1 I I I IIIIII IIIII Pllllllll JOHN M. GRAY Patented June 20, 1950 a piie noaiuaais, 1947-, Serial No.---748,-607- 1. This invention. relates. .tonelectronic,ph se.filer .tectors, andmore.particularlyin.ampl yin el tronic. phase .detectors of. the-variety em yin cathode gating .toiobtain.thedes hed phase det ction.

a ri ary..obiectotthis. rentionisto pr r a. phase vdetectoricapafibledef..deilept i phase i ferences between-any pair of; alternating; current signal voltages. which are. .eY. .,.harmQnics of an alternating-current reference voltage.

Another obj ect ofthis inventionnia. op t vide anamnlifyhq phase deteeto s fithe .varie v er scribed-Which is readily. adantablaforpha e d tectionof ,error signals in .datatransmission systems, particularly.ma nesym cutcsy s ems,-

Qther ;,objects.,ar.1d. advanta es o this entio will be appa nt from the..follow a es r p i and drawings in which 4 Fig. 1.,is a schematic diagram of the proposed invention; and

Fig. 2 is a group of .waveformsof voltages press is he mbe im ewi F a- "Assho'wn inFig. 1, a positive high-voltage direct-currents0urce5 with a suitable ground connection connects with the plates Sand. 1 of the cathode-gated amplifying phase detector. vac.- uum .tubes 8 and.9 throughthe plateload 11esistors.-I0;and II. The platesfiand I are also directly connected, to. a. conventional differential indicatonor control device ,I 2 through the terminals 3.,and4- Condensers l5. and l6 are connected loetweenthe plates 6. and 1, respectively, and ground. Out-of-phase voltages which are to be phase detected are coupled to the grids l1 and I8 of the vacuum tubes 8 and 9, through terminals l3 and 14, from the source of these voltages l9 which are even harmonics of the fundamental frequency of the alternating-current reference voltage source 20. Said source of even harmonics could be the error signal output in a magnesynto-autosyn system. An unfiltered full-wave rectifier 2| is provided comprising the transformer 22 connected in a conventional manner between the alternating-current source 20 and the rectifier tube 23. The fundamental frequency could be the excitation source for said magnesyn-toautosyn system. The positive unfiltered output voltage is connected to the common junction of the cathode return resistors 24 and 25 for the cathodes 26 and '21 of the vacuum tubes 8 and 9, respectively. Also connected to this junction through a bleeder resistor 28 is a negative highvoltage direct-current source 29 with its suitable ground connection. It is to be understood that proper bias is provided for the vacuum tubes 8 2. and 9 0X ..p 0per. selection ofgi .resistorsz :and;1emplov entof a theconventional ibiasing cimuitsi Y The. operation of-theuapparatus :will .be. de: scribed with reference to-the: embodiment of 1 and the voltagewaveforms off;Fig-.. 2 in which waveform 3.1 represents.- the, neference.) voltage from the-.soureeid; waveforms. 32 and .3211; the voltage atithe; grid., l]-;.- 33 and; 3,31, themoltage at the gridJB; waveform. 34.- the voltageiatvthe junction ofthecathoderesisttlrs 24,. and :2 5,; wave.- form 35, thevo1ta e .on. theplate 1;; .and-swave: form .36, -the...v.oltage Qmthe. p1ate..-.-; Theiwaver forms 32 iand.3,3.;must havethe phaseirelationship with respect to the; fundamental 3i ,as. showmbv Fig. 2 i.- e., successive, positive amplitnde .peaks of the Waveform Blrandsuceessive negatiiIe-amr plitude peaks of the.=Wayefprm,u33 :mustrperiodically occur Substantiallyuate the -zero points of the fundamen al 31;, orinthe hase; reversed operation successive .negativeamplitudeipeaksmf the waveform Bland successivezpositiveamplittilde peaks ofthe waveform.firmust eniodfcally occur substan ially at. thuzero points .of'; the fundamental 3L; hfisea hhse relatiqnships-aoce our dev esp e ing. on masnetim excitation by an alternatin sourceof voltagesparticularly .autosyns. The flattened; portionjof iwaveforim 3-4 isthe result of the, direct-current,component from Crsource 29,: i. e. the, voltage at the June.- tion rem i s o v as shownatad andthenattened portion occurs when the A..C.5vo1tage;.from source 20 is insufficient to overcornethenegative bias tof source;29;.and, permit irectifiergvn to. conduct.

The instantaneous combination of the waveforms 32 and 33 with the waveform 34 of the voltage at the junction of the cathode resistors provides a representation of the instantaneous grid-to-cathode voltage of the vacuum tubes 8 and 9, respectively. Waveform 34 has the waveforms. 32 and 33 superimposed for visual combination at any point in time. The vertical distance between the two horizontal broken lines represents the cut-off voltage of the vacuum tubes 8 and 9. The grid bias on tube 8 is measured by the algebraic difference between the instantaneous value of wave 32' and wave 34. The bias on tube 9 is similarly obtained by the difference between wave 33' and wave 34. Thus, it will be seen that conduction in either tube can only take place during the periods indicated between the lines of each pair of vertical broken lines, since only during that period is the bias less than outoff. Furthermore, referring to Waveforms 32' and 34, it will be seen that tube 8 will not conduct 3 during the entire period shown since the bias on grid I! always exceeds cut-off. Referring now to curves 33' and 34, it will be seen that tube 9 will start conducting at the beginning of the first period, when the algebraic difference between wave 33 and wave 34 is less than cut-off, and will cease at the end of the first period when the algebraic difference is greater than cut-off. Thus, the Voltage on plate 1 during said period will be of the form indicated at 35. If the time constant of resistor II and condenser I6 is selected to be several times the period of the unfiltered rectifier wave 34, then the voltage at plate 1 will have increased to only a portion of its original value before conduction of tube 9 again occurs, as shown in curve 35. Thus, the condenser I6 acts as a filter to filter out the cycles variations of the plate voltage of plate 1 and, as a result, the plate i maintains a substantially constant low direct current level, whereas plate 6 remains at a high level as shown at 36. Resister I and condenser [5 are similarly selected so that the reverse condition will exist on the plates 6 and 1 if the phase of the voltage waveforms 32 and 33 were reversed.

The direct-current voltages appearing at the plates 6 and 7 are then utilized to operate the differential indicator or control device 12 in accordance with the phase of the incoming signals to the grids l1 and I8. In the example depicted, a differential indicator will be deflected from its null point in one sense, whereas under conditions of phase reversal of the even harmonics signals, the differential indicator will be deflected from its null point in the opposite sense, thereby presenting to an observer an indication of the phase of the even harmonic signals.

It can be seen that this device will operate on any pair of substantially 180 related even harmonics of the reference frequency if the phase relationships are such that said even harmonics are phase related to the fundamental frequency so that either the positive or negative amplitude peaks of one of said harmonics and the corresponding negative or positive amplitude peaks of the other of said harmonics periodically occur substantially at the zero points of said fundamental; and further, varying amplitudes of the harmonic frequencies will produce a proportional variation in the indication or control provided by the device 12.

What is claimed is:

1. In an amplifying phase detector for com- 4 paring the phases of a wave from a source of fundamental frequency and a wave from a source of frequency evenly harmonically related to said fundamental frequency, the combination comprising: a pair of vacuum tubes having a common cathode connection and input circuits connected toopposite ends of the source of harmonics, respectively, a source of anode potential operatively connected to each of said tubes; and means responsive to the source of fundamental frequency and connected to said cathode connection for controlling the conduction of said tubes.

2. The combination according to claim 1 wherein said controlling means comprises a fullwave rectifier having its output connected to said cathode connection.

3. The combination according to claim 2 wherein said controlling means further comprises a source of direct current potential connected to said rectifier for preventing conduction of said rectifier during its complete cycle.

4. The combination according to claim 1, said tubes having output circuits, respectively, and a time sensitive network connected in each of said output circuits.

5. In combination with a source of alternating current of a fundamental frequency and a source of even harmonics of said fundamental frequency; an amplifying phase detector comprising: a pair of vacuum tubes having a common cathode connection, said tubes having input circuits connected to opposite ends of said source of harmonics, respectively; rectifier means responsive to said source of fundamental frequency and connected to said cathode connection for controlling the conduction of said tubes; and indicator means connected between the output cir cuits of said tubes. JOHN W. GRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Howes May 13, 1947 

